The present invention relates to grass and weed trimmers of the type wherein a plastic filament or blade is rotated at a relatively high rate and allowed to engage and cut the grass or weeds.
In recent years, various grass trimmers utilizing a plastic filament which is fed from a rotating head or the like have become very popular. Such trimmers are available in a wide variety of shapes and sizes and may be both electrically powered from a cord or driven by a self-contained engine. Such trimmers are normally utilized to augment conventional push or riding-type lawnmowers in areas where the terrain is too rough to take a lawnmower or for trim work in areas which are not easily accessible to a regular lawnmower.
Certain professionals in the lawn keeping business are required to use trimmers of this type much more frequently than other users. For example, caretakers of cemeteries must often cut grass near cemetery markers which cannot be closely approached by lawnmowers. Because of the volume of trimming which must be done in areas such as cemeteries and because many of such trimmers must be carried, users typically become tired very quickly. For this reason, there have been attempts in the past to design a grass trimmer with a support wheel which would allow the user to easily guide the rotating heads to the areas which need to be cut, yet the wheel would allow the trimmer to be sufficiently supported so that the user would not become tired too quickly. Such a trimmer is shown in the U.S. Pat. to Green, No. 4,033,098. While the device shown in the Green reference was an improvement over the prior art, the support wheel was positioned away from the rotating head and this made positioning of the head somewhat cumbersome.
In order to allow best control over the inclination and position of the rotating head, applicants determined that it would be best to have the wheel positioned as closely as possible to the rotating head and, in particular, directly beneath it, if possible. This, of course, presented problems in the design of such a trimmer, since the head had to be able to rotate freely without rotating the wheel and/or hitting the wheel during rotation.
Lawnmower structures having multiple wheels, especially riding lawnmowers, have been previously manufactured with a rotating blade surrounding a wheel of the structure, for example U.S. Pat. No. 4,084,395. However, because lawnmower structures have multiple wheels in contact with the ground, the rotating cutting mechanism is basically designed to rotate only in a horizontal plane. Because of this, the operator cannot rotate the cutting head from side to side to get closer or further from the ground as necessary and mobility is somewhat hampered since there is normally a substantial turning radius associated with a multi-wheel riding or push mower and/or it is relatively difficult to use a multi-wheeled machine where a great number of tight turns must be made, such as when cutting around a cemetery headstone and fencing. On the other hand, applicants have found that a single wheel trimmer allows both the benefit of simple height adjustment of the cutting mechanism necessitated by changes in terrain and the like by either rotating the trimmer from side to side or front to back about the wheel and also provides great mobility since the radius of turn for a single wheel vehicle is normally quite small compared to a multi-wheel vehicle.